The shim ratio used in leveling a motor mount is defined as which of the following?

• A. The distance between mounting bolts divided by the effective length of the motor shaft
• B. The distance from motor base to the top mounting point
• C. The sum of mounting bolt diameters
• D. The height of the motor shaft

Answer: (A)

Shim ratio in leveling a motor mount is about how the mounting geometry translates shim thickness into tilt through a lever effect. The distance between the mounting bolts acts as the lever arm that converts a shim height into angular tilt, while the effective length of the motor shaft serves as the other lever arm that resists that tilt. Expressing this as the ratio of bolt spacing to shaft length captures how sensitive the leveling is to shims: larger bolt spacing or a shorter shaft length increases tilt for the same shim thickness. The other options describe dimensions that don’t reflect this lever relationship—the vertical distance from base to top mounting, the sum of bolt diameters, or the shaft height don’t define how shim height produces angular misalignment.